1. Field of the Invention
The present invention relates to a surface acoustic wave device manufactured by dicing a piezoelectric wafer and a method of manufacturing the surface acoustic wave device and, more specifically, to a surface acoustic wave device having a package structure with an outline edge of a diced piezoelectric substrate serving as an outline edge of the product, and a manufacturing method of the surface acoustic wave device.
2. Description of the Related Art
A package structure having an outline edge of a piezoelectric substrate serving as an outline edge of the product is implemented in a surface acoustic wave filter used in an RF stage of a cellular phone. This arrangement promotes miniaturization of the product as the surface acoustic wave device. The number of surface acoustic wave devices that can be produced from the piezoelectric wafer is also increased.
Japanese Unexamined Patent Application Publication No. 2003-37471 to be discussed below discloses an example of such a surface acoustic wave device.
FIG. 7 is a sectional front view of the surface acoustic wave device described in Japanese Unexamined Patent Application Publication No. 2003-37471. The surface acoustic wave device 101 includes a piezoelectric substrate 102. An electrode structure including an IDT electrode 103 is formed on one surface of the piezoelectric substrate 102. Pad electrodes 104 and 105 electrically connected to the IDT electrode 103 are formed on the one surface of the piezoelectric substrate 102. A resin layer 106 is arranged to be opposed to the piezoelectric substrate 102. A plurality of through-holes are formed in the resin layer 106 and internal circumferences of the through-holes are coated with conductors 107 and 108. Lower ends of the conductors 107 and 108 are electrically connected to external electrodes 109 and 110. Upper ends of the conductors 107 and 108 are electrically connected to pad electrodes 111 and 112.
A precision layer 113 is formed on a top surface of the resin layer 106. The precision layer 113 surrounds a region including the top ends of the conductors 107 and 108 and the pad electrodes 111 and 112. Resin layers 114 and 115 are arranged in a surrounding region of the pad electrodes 111 and 112 for height adjustment to be flush with the top surface of the precision layer 113.
Light curing resins 116 and 117 are used to bond together the resin layer 106 and the piezoelectric substrate 102 with the resin layer 106 and the piezoelectric substrate 102 opposed to each other as illustrated. In the bonding operation, the light curing resins 116 and 117 are arranged to surround a cavity S that causes a surface acoustic wave not to be impeded. Through conductors 118 and 119 are formed within the light curing resins 116 and 117. The through conductors 118 and 119 electrically conduct the pad electrodes 104 and 105 to the pad electrodes 111 and 112.
A large-scale piezoelectric wafer is prepared to manufacture the surface acoustic wave devices 101. In order to manufacture a plurality of surface acoustic wave devices 101 on the piezoelectric wafer, a plurality of electrode structures, each including the IDT electrode 103 and the pad electrodes 104 and 105, are formed. The resin layer 106 is then bonded to the piezoelectric wafer with a light curing resin interposed therebetween. A laminate body thus constructed is diced in the direction of thickness into a plurality of surface acoustic wave devices 101. A shape of the surface acoustic wave device 101 thus obtained is identical in plan view to the piezoelectric substrate 102.
In accordance with the method of manufacturing the surface acoustic wave device 101 described in Japanese Unexamined Patent Application Publication No. 2003-37471, a dicing operation is performed on a mother laminate after the mother laminate is produced. In the dicing operation, elements to be diced include not only the piezoelectric wafer but also the light curing resins 116 and 117, a synthetic resin layer, and the resin layer 106. To form the through conductors 118 and 119 through electroplating, a wiring pattern for supplying voltage to the plating is formed. Since such a wiring pattern straddles adjacent surface acoustic wave devices on the piezoelectric wafer, the wiring pattern is partially diced in the dicing operation.
Since cured adhesives, metals, and the like are cut by a dicing blade, the dicing blade is more subject to wear. When a plurality of surface acoustic wave devices are cut from the laminate, a relative large number of dicing operations are performed. The dicing blade is thus worn, leading to failure to perform a high precision dicing and a reduction in the dicing speed.